The group, named "Fishermen of the Night," had no idea what to expect that evening two years ago, Mr. dos Santos recalls. Since then, they have seen men killed. They have been threatened with death. But God has sent them as emissaries, they say, to stop the violence that is suffocating many of Brazil's poor communities.

"You cannot stutter," adds his wife Christiane in their modest home in Mangueira, a favela that winds up the side of a hill, where homes seem like blocks stacked upon one another. "You say, 'I am from Jesus.' There is no room for doubt."

The group's core purpose is not to fight crime, but to convert as many as possible. More law and order is often a byproduct.

In Rio's favelas,crowded with men and women on the margins, they find fertile ground. To outsiders they are called "the Evangelicals," and for the most part, people here don't challenge their missionary work.

In fact, Pentecostals – for theological, cultural, and personal reasons – have apparently won the respect of the same criminals who may think little of shooting a lifelong neighbor.

So in a city that is considered one of the most dangerous in the world, which registers 6,000 murders a year, and where the police and military are distrusted at best, Pentecostals are among the few who are facing up to organized crime.

"They are viewed as staying out of all the conflict that exists in the world. They live separate from the world, not inside the factions that are everywhere else," says Patricia Birman, an anthropologist at the State University of Rio De Janeiro. "They can intervene because of that."

In absolute numbers, Brazil, the region's biggest country, has more Pentecostals than anywhere else in Latin America. Over 10 percent of the population identified itself as Pentecostal in Brazil's 2000 census, double the figures from a decade earlier. According to a 2006, 10-country survey of Pentecostals by the Pew Research Center, a non-partisan think tank in Washington, nearly 21 percent of urban residents surveyed identified themselves as Protestant, the majority Pentecostal.

It takes only a trek into a favela on a Sunday night to understand the traction of the movement.

In the dark, winding alleys of the Mangueira favela, joyous music pours from Pentecostal churches, most of them drab cement structures on the outside but full of dance and song within.

To get to dos Santos's church, Assembly of God New Zion, visitors pass young teens with guns guarding homes and a local drug den where a pile of white cocaine powder sits on a table in full view. Before the church was founded seven years ago, it was an abandoned building.

One reason Pentecostals can approach drug traffickers is that so many of them were once violent felons themselves. Some have committed murder. Their pastors have served time. And, reborn, they now believe their calling is to bring the word of God to the same streets they once terrorized.

Dos Santos converted to Pentecostalism after more than 15 years dealing drugs and robbing passengers at knife-point on city buses. His pastor, Marcos Lourenço, served time for drug trafficking. Pastor Lourenço points to the man sitting to his left. "He just got out of jail; his wife is still there," he says. He rests his hand on the man to his right. "This used to be my No. 1 enemy."

On a recent night, Lourenço works his tiny congregation into a frenzy of "glorias" and "amens." Men and women squeeze their eyes shut as Lourenço, a squat man with a baby face, breaks into a sweat. They all dance to drums, a keyboard, and a tambourine, played by a group of teens. They are off-key, but no one seems to care or notice. "Oh gloria, gloria, gloria," shouts one young woman, clutching her chest.

"How can people change so much? I ask myself that all the time," muses Lourenço.

Many of today's Pentecostals were brought into the faith by other Pentecostals. But new converts also come on their own to the doors of churches or the homes of pastors. For those in gangs, who conclude that their only way out is death or jail, conversion offers a third option, says David Smilde who studies the phenomenon in Caracas, Venezuela, and is the author of "Reason to Believe," published this past summer.

"It's a way of stepping out of an impossible situation; they are no longer feared by the [criminal] network," says Mr. Smilde, a sociologist at the University of Georgia. Where there is little police presence or institutional support, he says, "Pentecostalism is one way out."

"The only path to live in peace is this path," agrees Thiago de Castro Cosia, a young convert from New Zion. "It's the only way to make your enemies your friends. It's the only way to be free."

It is a drastic mind shift, but it is supported by theology. Because many Pentecostals consider themselves "reborn," they are able to step away from their past sins, and reemerge with a new identity. They believe the devil's hand is behind urban violence and drugs, and often turn to exorcism to root out evil.

The Roman Catholic Church, on the other hand, says Ms. Birman, focuses on the larger idea of civic consciousness, such as drawing attention to the root causes of violence. But for people faced with crime every day, the response is often seen as institutional or out of touch.

Academics who study this phenomenon say that Pentecostals are able to penetrate areas where even census workers won't go, not just because they hail from the same tough neighborhoods, but because most churches are independent, grass-roots efforts – unlike the Catholic Church, which is run under strict hierarchy that starts at the Vatican.

"It works precisely because it is informal," says Clara Mafra, an anthropologist at the State University of Rio de Janeiro. "They don't have to ask someone's permission. The Holy Spirit talks to them."

Pastors are largely autonomous, so an idea that comes to them in the middle of the night can be implemented the next day. It is a format that lends itself to a more local, and often more innovative, response.

"The Catholic Church is slow. They repeat the same model in different areas of the city, if you have a lot of violence or not," says Ms. Mafra. "The Pentecostals, they try different solutions and different arrangements."

Gang members leave Pentecostals alone because, although they don't necessarily practice any religious doctrine, they still overwhelmingly believe in God, say researchers. Catholicism has traditionally reflected the political elite here, who are seen as having done little to combat crime. Pentecostals are seen by the community as operating in a separate, uncorrupted sphere, says Birman.

If converting is a strategic way out for many young men, some question how deep and lasting their faith is. For every convert there is another who is leaving the religion, as backsliding is rampant. But Smilde says many do end up as long-term believers. Their entire sense of self and purpose changes, he says, whether they've converted to leave a gang, because their wives made them, or simply because they were drawn to God.

On a recent evening, a group of young men from the New Zion church sits in a circle sharing testimonials, the stories of their conversion. They are dressed in tennis shoes and running pants, not unlike the men outside carrying guns and dealing drugs.

They say the nerve they had as gangsters came from the devil. "I feel more courageous now; more like a man," says Hugo Leonardo da Silva, a 22-year-old with a young wife and daughter.

His path to Pentecostalism was not easy.

He tried to convert many times but says he lacked strength. Even now, he says the easy money and temptation of gang life is around him every day.

He deals with it by staying away, he says, "unless it is to spread the word of God."

That is where the two worlds converge for "Fishermen of the Night."

"Who are you?" barked a gang member, seeing dos Santos's group approaching them in the middle of the night, right at the spot where they used to carry out their briskest drug sales. Dos Santos stood in the front, and was pushed to the ground with the butt of a rifle.

"We come with the word of God," dos Santos said, suddenly surrounded by 40 men from the Red Command, one of the fiercest factions operating in Rio de Janeiro. The Pentecostals prayed, trancelike, as they called out for God to reach the gang. dos Santos says he doesn't remember what he was saying, or what was happening around him. He kept repeating, "You are not alone, you are with Jesus." Someone suggested they were spies for the police or a rival drug gang.

Dos Santos says he can stay calm in such situations because he carries the shield of God, but certainly his personal experience in a gang helps him.

He began using drugs at age 8, and quickly climbed the ranks of one of the local gangs. He and Christiane married when he was 16, she was 13. It wasn't until his life was threatened – by his own gang – that he converted.

He walks the same streets today, but now with a Bible in his hand. On a recent day he walked past the drug den he once protected. Nearby is an apartment that he rents out to tenants today. He and his wife, who have three young children, also own a popular hamburger joint at the edge of Mangueira. He still lives carefully – refusing to talk about the violence in his neighborhood while in public, even though he says he always walks with faith in God.

He doesn't know how long after he was shoved to the ground that the group's leader walked onto the scene, and held out his hand to dos Santos. "You aren't spies; if you were I'd kill you all. You are believers for real, you are welcome here any time," he said to him.

"One day I was in the same place," dos Santos explains later, when asked why he puts himself at such risk. "God got me out of this place."

That night they preached to the Lord. But not every intervention helps people put the thug life behind them. That gang leader was killed a couple of months later.

Few situations are as dangerous for the "Fishermen of the Night" as that night two years ago, but it's never easy. They say they intervene when God tells them to, which could be several times one month, none the next.

But are they having a lasting impact? John Burdick, an associate professor of anthropology at Syracuse University, says that pastors will take credit for reducing crime in their neighborhoods, but he says that no academic has been able to clearly show that this is an effective tool in the long run.

Still, few doubt that on a small scale they are making a difference.

Their mission is to convert as many Brazilians as possible, and the poor and disadvantaged are their perfect targets. Favelas, where many potential converts live, have traditionally fallen off the political radar, says Jurema Batista, the president of a government-run agency child and adolescent rights. In that sense Pentecostals are doing a job that the government is not. "They are filling a role that no one else is."

"They regard themselves as engaged constantly, as getting [nonbelievers] out of the drug trade, alcoholism, aggressive behavior, and all the things that lead to fights and violence," adds Professor Burdick. "And as they do convert, their behavior does change. They stop being involved in a whole array of things that generate violence, directly or indirectly."

They also offer hope to people who thought there was none left.

Dos Santos, who drives around in a 1991 brown Ford station wagon with a bumper sticker that reads "Exclusive Property of Jesus," says he often has little idea whether the criminals they preach to end up converting.

Probably most don't, he admits. But the work of the "Fishermen of the Night" has spread around town. And one letter he received gives him all the proof he needs to forge ahead.

It was a couple of years ago, on a Friday night. A gang member called his home, telling dos Santos that he felt he was going to get shot dead soon unless he quit. He asked dos Santos for help.

This time dos Santos had no time to fast, which the group usually does for two days to purify body and soul before setting out on an intervention.

He gathered as many people as he could. They arrived at 1:30 a.m., while the gang was still eating dinner near the spot where the drugs were sold. En route, Christiane, dos Santos's wife, says she had a vision of the gang member being buried.

When they arrived at the scene, she told the gang member about her vision, and he began to weep. They prayed for him for hours, and left him a Bible. He handed them his rifle.

Two months later, dos Santos received another call from the man. But this time it was to invite dos Santos to a new church.

The gang member had become a pastor. That was two years ago. "I still get goose bumps," dos Santos says, the flesh rising on his arms.